Hi once again Saab Dastard.
I'm sorry but I have given the wrong impression for you to deduce that it was CrapCleaner which wiped off the 30Gb each time. I still have absolutely no idea how or when the 30Gb disappeared each time. I just discovered that the hard disc occupation had dropped by the time I looked at it on occasion. I usually looked at the machine when I wanted to do a general clean up, including CrapCleaner.
Immediately before my wife's return Defraggler showed that a little over 40Gb of hard disc space was used and about 65Gb free. 24 hours later, with her normal usage in the meantime, opening Defraggler showed that the hard disc's used space now amounted to 62Gb. I ran CrapCleaner and it cleaned out not very much, about 140Mb.
I then ran a "Quick Defrag" which reduced a starting 13% fragmentation with 91 fragmented files totalling 7.5Gb and with 434 fragments to still 13% fragmentation, 6 fragmented files still totalling 7.3Gb but only 74 fragments. The total hard disc occupation was still about 62Gb.
I then ran a "Full Defrag" and the stats, as time went by, were as follows:-
30 minutes, HDD occupation up by 2Gb to 64Gb, fragmentation figures unchanged
60 minutes, HDD occupation up by 4Gb to 66Gb, fragmentation figures unchanged but process shown as 34% done
70 minutes, HDD occupation up by 6Gb to 68Gb, fragmentation figures unchanged
120 mins, 8Gb to 70Gb, now 352 fragments but still 6 files fragmented
150 mins, almost 10Gb to 71.5 Gb, now 52 fragments and 4 fragmented files, 4.6Gb, "Finished"!
I then ran Windows Defragmenter which finished, satisfied with the tidy-up, after only five minutes.
I can imagine no explanation. It's worth noting that on absolutely each of the dozens of times I have run Defraggler on my own XP machine, the figures for used and unused space on my disc remain effectively unchanged throughout the process and it ends with 0% fragmentation, 0 fragmented files and 0 fragments.